iOS 16: `volume` for critical notification sounds not working anymore

[robertklep]

iOS device model, version and app version

Model Name: iPhone 12 mini Software Version: iOS 16.0 App version: 2022.8 (2022.387)

Home Assistant Core Version

Home Assistant Core 2022.8.6

Describe the bug The volume property for critical notification sounds doesn't work anymore. This might be an iOS 16 bug, see "Additional context" below.

To Reproduce Send a critical notification at 10% level:

service: notify.mobile_app_<your_device_id>
data:
  message: "Hello World!"
  data:
    push:
      sound:
        name: "default"
        critical: 1
        volume: 0.1

Expected behavior Critical notification sounds should be played at the volume specified in the push notification.

Additional context

When the notification is received, the volume bar on the left side of the screen is shown and the volume seems to get set to what the volume property is set to. However, the sound itself gets played at a different volume regardless.

If I open an app that plays music (SoundCloud in my case), the music is played at proper system volume. After that, critical notification sounds are also played at that volume, hence my suspicion it might be an iOS 16 bug.